United States
Environmental Protection
Agency
Off ice of
Emergency and
Remedial Response
EPA/ROD/R09-91/070
September 1991
&EPA Superfund
Record of Decision:
Monolithic Memories (Advanced
Micro Devices - Arques) (National
Semiconductor), CA
-------
50272.101
REPORT DOCUMENTATION 11. REPORTNO.
PAGE EPA/ROD/R09-9l/070
4. 1111..nd~ SUPERFUND RECORD OF DECISION
Monolithic Memories (Advanced Micro Devices - Arques)
(National Semiconductor), CA
First Remedial Action
7. Aulhor(s)
I ~
3. RecIpient's Ac:cnaIon No.
5. Report D818 >
09/11/91
6.
6. Purfonnlng OrganlD1!on Rept. No.
8. IWforming OrlialnIDlIon Name and Add....
10. Projec1lTaaklWork UnI1 No.
11. ContraC1(C) or Gran1(G) No.
(C)
1~ SponaorIng Orllanlza1lon Name and Addre..
U.S. Environmental Protection
401 M Street, S.W.
Washington, D.C. 20460
(G)
13. Type of RIIpOI1& PerIod Covered
Agency
800/000
14.
15. > SUpplemen1ary No,"
16. Ab81rsc1 (UmIt: 200 _Ida)
The Monolithic Memories (MM) site is a former semiconductor manufacturing facility
located in Sunnyvale and Santa Clara, California. Land surrounding the site is used
for commercial and light industrial purposes. The site lies within the confined area
of the Santa Clara Valley ground water basin, which consists of various upper and
lower aquifer zones. Ground water from this basin provides up to 50 percent of the
municipal drinking water for Santa Clara Valley residents. Remediation of the MM
site has been combined with another National Priorities List (NPL) site, National
Semiconductor (NSC), because both sites contribute to the same ground water
contaminatio~ problem. The combined remediation has been divided into two Operable
Units (OUs). This Record of Decision addresses OU1, which consists of three
subunits. Subunit 1 includes the 60-acre NSC facility, which contains more than 20
buildings used for administrative offices, laboratories, and semiconductor
manufacturing; and the 10-acre United Technology Corporation facility, which was used
to develop and test rocket propellants. Subunit 2 includes the MM facility,
currently owned by Advanced Micro Devices, and consists of buildings used for office
space and semiconductor production facilities. Subunit 3 consists of the areas
..
(See Attached Page)
17. Documen1 Analysis L Descrlp10ns
Record of Decision - Monolithic Memories (Advanced Micro Devices - Arques)
(National Semiconductor Corp.), CA
First Remedial Action
Contaminated Media: soil, gw
Key Contaminants: VOCs (benzene, PCE, TCE, toluene, xylenes), other organics (PARs,
phenols)
b. Idenllti8r8lOpen-Ended Terms
Co COSA 11 FIeIdIGr~
'8. Av8llsbllty SIa1emen1
18. Sec:uity ClaM (Th18 Report)
None
20. Sec:uity Cis.. (Th18 Page)
None
21. No. 01 Pages
50
->-
I
~ Price
(See ANSl-Z38.18)
See IM/nIcIIOM on Rew,"
-
(Formerty NT1S-35)
Depar1ment of Conwnerce
'-'-.
-------
EPA/ROD/R09-91/070
MonOlithic Memories (Advanced Micro Devices
(National Semiconductor Corp.), CA
First Remedial Action
- Arques)
Abstract (Continued)
downgradient from Subunits 1 and 2 and extends to the leading edge of the contaminant
plume. Semiconductor manufacturing activities took place onsite at NSC beginning in
1967, and at .MM in 1970, and continued until 1989. Virgin solvents and acids used in
semiconductor manufacturing processes were stored in above-ground tanks and storage
drums. Waste solvents were stored in underground and above-ground tanks, and acid wastes
were treated in underground and above-ground tanks or underground neutralization sumps.
In 1982, NSC and MM conducted preliminary assessments of soil and ground water near
underground storage tanks and sumps, in response to a state-initiated storage tank leak
detection program. As a result, both NSC and MM removed tanks, sumps, and soil from
areas containing elevated concentrations of solvents. In addition, in 1984 and 1986, NSC
installed offsite and onsite ground water extraction systems, and MM installed onsite
extraction systemS in 198q and 1988. This Record of Decision (ROD) addresses remediation
of contaminated soil on the facility property and ground water in the upper aquifer zone
as OUI. OU2 will address remaining soil arid ground water problems associated ,with the
western portion of the ground water contaminant plume. The primary contaminants of
concern affecting the soil and ground water are VOCs including benzene, PCE, TCE,
to~uene, and xylenesi and other organics including PAHs and phenols.
The selected remedial action for this site includes treating contaminated soil in
Subunits 1 and 2 onsite using soil vapor extraction, with carbon adsorption to control
emissions, if requiredi excavating and surface aeration of contaminated soil, if
necessary; pumping and onsite treatment of contaminated ground water by expanding the
existing extraction system and adding an ozone oxidation treatment system to the current
air stripper treatment systems; controlling air emissions from the air strippers using
carbon treatment, if necessary; discharging the treated ground water onsite to storm
sewers; monitoring ground water; and implementing institutional controls including deed
restrictions. The e?timated preEent worth cost for this remedial action is $8,400,000,
which includes a 30-year operation period. O&M costs were not provided.
PERFORMANCE STANDARDS OR GOALS: Chemical-specific clean-up goals for soil and ground
water are based on the more stringent of State MCLs, Federal MCLs, non-zero MCLGs, and
site-specific standards based on an HI < 1 and a calculated ~ancer risk of l(j6 to 10-4 .
Chemical-specific goals for soil include total VOCs 1 mg/kg (site-specific) and
PAHs 10 mg/kg (site-specific). Chemical-$pecifi~ goals for ground water include benzene
1 ug/l (State), phenol 5 ug/l (State), PCE 5 ug/l (State), TCE 5 ug/l t~at~), and
xylenes 175 ug/l (site-specific).
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ADVANCED MICRO
RECORD OF DECISION
JOINT SUPERFUND SITES
NATIONAL SEMICONDUCTOR AND
DEVICES - ARQUES (FORMERLY MONOLITHIC MEMORIES)
OPERABLE UNIT 1
SUNNYVALE AND SANTA CLARA, CALIFORNIA
SEPTEMBER, 1991
U.S. ENVIRONMENTAL PROTECTION AGENCY
REGION 9
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PART
I
I
I
I
I
II
II
II
-
II
II
1.0
2.0
3.0
4.0
5.0
1.0
1.1
1.2
1.3
1.4
1.5
1.6
2.0
2.1
2.2
3.0
4.0
4.1
4.2
4.3
5.0
5.1
5.2
CONTENTS
SECTION
PAGE
PART I:
DECLARATION
Declaration
6
statement of Basis and Purpose
6
Assessment of the site
6
Description of the Remedy
6
statutory Determinations
7
PART II:
DECISION SUMMARY
Site
Names, Locations, and Descriptions
Site Names and Locations
Site Descriptions
Regional Topography
Adjacent Land Use
Hydrogeology
Water Use
9
9
9
12
13
13
15
site History and Enforcement Activities
History of Site Activities
History of Site Investigations
17
17
18
Community Relations
19
Scope and Role of the Response Action
Scope of the Response Action
Selected Response Action
Role of the Response Action
Summary of site Characteristics
Soil and Groundwater
Air
20
20
20
21
22
22
25
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II
6.0
6.1
6.2
6.3
II
7.0
7.1
7.2
7.3
II
8.0
II
9.0
9.1
9.2
II
10.0
II
11. 0
III
1.0
III
2.0
ATTACHMENT. A:
ATTACHMENT B:
Summary of Site Risks
Human Health Risks
Environmental Risks
Conclusion
Description and Consideration of Alternatives
Applicable or Relevant and Appropriate
Requirements (ARARs) for Alternatives
Considered at AMD-Arques and NSC
Operable Unit 1 Alternatives for the
AMD-Arques and NSC Sites
Uncertainty in Achieving Cleanup standards
Comparative Analysis of Alternatives
The Selected Remedy
Description
Uncertainty in the Remedy
statutory Determinations
Documentation of Significant Changes
PART III:
RESPONSIVENESS SUMMARY
Introduction
Responses to Comment
RWQCB'Responsiveness Summary
Administrative Record Index
25
25
32
33
33
33
36
41
42
45
45
46
47
48
49
49
'-'_u"-"-
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TABLE
1
2
3
4
5
6.
LIST OF TABLES,
TITLE
Chemicals and Media of Concern - Subunits 1 and 3
Chemicals and Media of Concern - Subunit 2
Summary of Potential Health Risks -
National Semiconductor Site
Carcenogenic Risks Associated with Proposed
Ground Water Cleanup Standards - Subunit 2
Non-Carcinogenic Risks Associated with Proposed'
Ground Water Cleanup Standards - Subunit 2
Cleanup Standards and ARARs - AMD/Arques and
NSC Sites Operable unit 1
38
-
""':...... ~-- ~-" ..,'.:
PAGE
27
28
29
30
31
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LIST OF FIGURES
FIGURE TITLE PAGE
1 Site Map 11
2 Hydrogeologic Features 14 .
.J
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PART I.
DECLARATION
1.0
SIT~ NAME AND LOCATION
National Semiconductor corporation
2900 Semiconductor Drive
Santa Clara, California
Advanced Micro Devices - Arques (Formerly Monolithic Memories)
1165 and 1175 Arques Avenue
Sunnyvale, California
2.0
STATEMENT OF BASIS AND PURPOSE
This Record of Decision ("ROD") presents the selected remedial
action for the National Semiconductor and Advanced Micro Devices -
Argues Superfund sites, Operable Unit 1, in Sunnyvale and Santa
Clara, California. This document was developed in accordance with
the Comprehensive Environmental Response, Compensation," and
Liability Act of 1980 (CERCLA) as amended by the Superfund
Amendments and Reauthorization Act of 1986 (SARA), 42 U.S.C.
Section 9601 et. sea.. and, to the extent practicable, the National
Oil and Hazardous Substances Pollution contingency Plan, 40 C.F.R.
Section 300 et. sea.. ("NCP"). The attached administrative record
index (Attachment B) identifies the documents upon which the
selection of the remedial action is based. The State of California
concurs with the selected remedy.
3.0
ASSESSMENT OF THE SITE
Actual or threatened releases of hazardous substances from these
sites, if not addressed by implementing the response actio~
selected in this ROD, may present an imminent and substantial en-
dangerment to public health, welfare, or the environment.
4.0
DESCRIPTION OF THE REMEDY
The entire area of groundwater contamination associated with these
and other non-NPL sites (the Study Area) has been divided into two
operable units. Operable unit 1 represents the areas that have
been thoroughly investigated, and for which enough information
exists to select a final remedy. See section 1.2 of the attached
Decision Summary for" a complete site description. An RIfFS is
underway for Operable Unit 2, and it will address the soil and
groundwater problems associated with the western portion of the
plume.
The selected final remedy for the National Semiconductor and
Advanced Micro Devices-Argues sites (Operable Unit 1) includes the
following elements:
o Groundwater extraction, to control further migration
6
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of site chemicals in the contaminated aquifers and reduce
chemical concentrations until cleanup standards have been
achieved.
o Treatment of extracted groundwater with air stripping
or ozone oxidation under Bay Area Air Quality Management
District (BAAQMD) permit or pursuant to OSWER Directive
9355.0-28.
o Discharge of extracted and treated groundwater to storm
sewers under National Pollutant Discharge Elimination System
(NPDES) permits.
o Soil Vapor Extraction (SVE) will be employed where vadose
zone soils present a potential continuing source of
contamination to groundwater or where shallow soils
represent a health risk due to direct contact. Shallow
soils at the AMD site are contaminated with semi-volatile
compounds and may require removal if they do not respond to
SVE. SVE will be conducted under a BAAQMD permit.
o Institutional Controls prohibiting the use of the A and B
aquifer groundwater and for controlling activities that
could endanger the public health or the environment.
In order to implement this final remedy for Operable Unit 1, the
currently operating extraction system will be expanded, and an
ozone oxidation treatment system will be added to the current air
stripper treatment systems. The air strippers and SVE will include
air emissions control (carbon treatment) if emissions exceed levels
currently permitted by the BAAQMD or requirements of QSWER
Directive 9355.0-28. NPDES discharges will go to storm sewers
which empty into the Calabazas Creek. Approximately 160 gallons
per minute (gpm) will be treated by air stripping and approximately
80 gpm will be treated with ozone oxidation.
Vadose. and shallow soil contamination at these sites will be
addressed by SVE. Contingent upon the inability of SVE to address
low volatility compounds, some excavation and surface aeration of
contaminated soils will be performed. If it is determined that
this additional effort is necessary, a permit from the BAAQMD must
be obtained.
5.0 STATUTORY DETERMINATIONS
The selected remedy is protective of human health and the
environment. Contaminated groundwater and soils will be restored
to health protective levels once cleanup standards have been
achieved, and until that occurs, direct contact exposure to
.contaminated media will be prevented with institutional controls.
The selected response actions comply with Federal and State
requirements that are legally applicable, or relevant and
-------
appropriate; primarily the drinking water standards (Federal and
State MCLs), Bay Area Air Quality Management District permit
requirements for air emissions, and the National Pollutant
Discharge Elimination System requirements for discharge of treated
effluent.
These remedial actions address the principal risks at the National
Semiconductor and Advanced Micro Devices - Arques sites (Operable
Unit 1) by removing and treating the contamination in soils
(primarily soil vapor extraction), and by removing and treating
contaminants in ground water (extraction with air stripper and
ozone oxidation treatment), thereby significantly reducing the
toxicity, mobility or volume of hazardous substances in both media
through treatment. Using soil vapor extraction and ozone oxidation
treatment utilizes permanent solutions and alternative treatment
technology to the maximum extent practicable and satisfies the
statutory preference for remedies that employ treatment that
reduces toxicity, mobility, or volume as a principal element. An
evaluation of the alternatives considered shows the selected remedy
to be a cost effective response.
Because the remedy may require 30 to 100 years to achieve cleanup
standards, a five-year review, pursuant to CERCLA Section 121, 42
U.S.C. Section 9621, will be conducted at least once every five
years after initiation of the remedial action to ensure that the
ongoing remedial action continues to provide adequate protection of
human health and the environment.
,—•h^-~
John Wisely Date
Deputy Regional Administrator
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PART II. DECISION SUMMARY
This Decision Summary provides an overview of the problems posed by
the National Semiconductor and Advanced Micro Devices - Arques
Superfund sites (Operable unit 1). It also includes a description
of the remedial alternatives considered, and the analysis of those
alternatives against Federal criteria. This Decision Summary
explains the rationale for the remedy selection and how the
selected remedy satisfies the statutory requirements of CERCLA.
1.0
SITE NAMES, LOCATIONS, AND DESCRIPTIONS
1.1
SITE NAMES AND LOCATIONS
National Semiconductor Corporation
2900 Semiconductor Drive
Santa Clara, Ca~ifornia
Advanced Micro Devices - Arques (Formerly Monolithic Memories)
1165 and 1175 Arques Avenue
Sunnyvale, California
1.2
SITE DESCRIPTIONS
The two sites, although listed separately on the National Priority
List (NPL), contribute to the same groundwater problem, and for
this reason, the investigation and evaluation of cleanup options
has been combined.
The study area comprising the two Operable units (see Figure 1,
page 11) contains. numerous sources of soil and groundwater
contamination in western Santa Clara and eastern Sunnyvale. Figure
1 shows the lack &f definition Qf the.western extent of groundwater
-contamination. An RIfFS is underway for Operable Unit- 2 and it
will address the soil and groundwater problems associated with this
area of the plume. -
Operable Unit 1 has been divided into three subunits for ease of
description, and to more efficiently address the unique aspects of
remediation particular to each subunit. Figure 1 shows the extent
of the plume in the study area and the areas that comprise the
three subunits of Operable Unit 1. The following text describes
each subunit.
Subunit One
-The National Semiconductor (NSC) facility at 2900 Semiconductor
Drive in Santa Clara occupies approximately 60 acres and contains
over 20 buildings used for administrative offices, laboratories,
and semiconductor manufacturing. The NSC site also inclu~es the
9
"""-... .-- ~- ...'.
p~-,-"--
, ~'...
-------
former United Technologies Corporation (UTC) facility which adds
another ten acres to the site and is located approximately 200 feet
northwest of the NSC facility. (NSC assumed responsibility for
cleanup of the UTC facility in 1987) These areas, and the area
downgradient of the NSC facility boundary to Arques Avenue, have
been designated as Subunit 1.
TheNSC facility property is bounded by the Central Expressway on
the north, the Lawrence Expressway on the east, Kifer Road on the
south, and by a property line about 1000 feet east of Commercial
Avenue on the west. NSC has manufactured semiconductors at this
facility since 1967. Virgin solvents and acids used in
semiconductor manufacturing processes were, or are, stored in
aboveground tanks and storage drums. Waste solvents have been
stored in underground and aboveground tanks; acid wastes have been
~------- -..
10
-------
?
~
~
N
I
o
.
SCALE IN fEET
seo
rORWER
UNITED TECHNOLOCIES
CORPORATION SITE
EX PLANA TION
o 0 ?O~
NATIONAL
SEt.lICONDUCTOR
SITE
. Extraction Well
.. Subunit 3 Proposed
Elltractlon Well
C8I Treatment System
~" Potentlol Source
a.; ~ Area Site
- ApproxImate
Lateral [dent 01
Known VOC PI"me.
~8oundorln 01
L-: Subunit.
LAVtfiENCE EXPRESSWAY
FIGURE 1. Subunits 1, 2, and 3 of Operable Unit 1 for the Advanced Micro-
devices-Arques and National Semiconductor Superfund Sites. Also shown is
the approximate lateral extent of the known VOC plume, Operable Unit 1
extraction well and treatment locations.
-------
treated in underground
neutralization sumps.
and
aboveground
tanks
or
. underground
The forme.r UTC facility, which is part of Subunit 1 and is
northwest of the NSC property, is bounded by the Central Expressway
on the south, Arques Avenue on the nort~, the Hewlett Packard (HP)
property on the west, and the O'Donnell Brigham property to the
east. The former UTC facility, which consisted of two buildings,
was used for research, development, and small-scale testing of
rocket propellants from 1960 to 1982. HP bought the property from
UTC in 1982, and removed the UTC buildings and auxiliary
facilities. HP subsequently constructed a park, conference
facility, and parking facilities at that location.
Subunit 2
The Advanced Micro Devices (AMD-Arques) facilities, which have been
designated as Subunit 2, consist of Buildings 1 and 2 on Arques
Avenue, and Building 3 at 1160 Kern Avenue. The AMD property is
bounded by Kern Avenue on the north, Arques Avenue on the south,
and is approximately 200 feet west of the Lawrence Expressway.
Semiconductor manufacturing operations were begun at the facility
by Monolithic Memories (MMI) in 1970. AMD acquired MMI and their
property in 1987 and assumed responsibility for continuing the soil
and groundwater investigations and remediation program for the AMD
facility.. Buildings 1 and 2 were used as office space and
semiconductor production facilities. Building 3 was originally
constructed for Amdahl corporation in 1972 and used to assemble
computer components. MMI leased Building 3 in 1974 and remodeled
it to hold offices and circuit-assembly laboratories.
Semiconductor production ceased in 1989 and Buildings 1 and 2 have
been unoccupied sin~e then. Building 3 is currently used as a
facility office.
Subunit 3
Subunit 3 consists of the areasdowngradient from Subunits 1 and 2,
and extends to the leading edge of the contaminant plume, which is
approximately 1400 feet north of Highway 101.
1.3
REGIONAL TOPOGRAPHY
The study area is located in the Santa Clara Valley which js a
gently sloping alluvial plain, flanked by the Diablo Range to the
east-southeast and the Santa Cruz Mountains to the west- southwest.
The study area is located toward the center of the valley. The
Santa Cruz Mountains are located several miles southwest of the
Study Area. San Francisco Bay is located approximately 6 miles
north of the study area.
12
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1.4
ADJACENT LAND USE
The study area is an industrial park setting, dominated by low rise
industrial buildings common in the electronics industry of Santa
Clara County. Mixed commercial and light industrial use is common
in the areas immediately surrounding the industrial park area.
Residential property lies at the northern edge of the study area;
some south of Highway 101 and west of Lawrence Expressway, and some
north of Highway 101 and east of the Lawrence Expressway.
1.5
HYDROGEOLOGY
Reaional - The study area is located in the Santa Clara Valley (see
figure 2, page 14) which extends southeast of San Francisco Bay and
is bounded by the Diablo Range on the northeast, and by the Santa
Cruz and Gabilan Ranges on the southwest. The Santa Clara Valley
is a large structural depression in the Central Coastal Ranges of
California. .The valley is filled with alluvial and fluvial
deposits from the adjacent mountain ranges. These deposits are up
to 1500 feet in thickness. At the base of the adjacent mountains,
gently sloping alluvial fans of the basin tributaries laterally
merge to form an alluvial apron extending into the interior of the
basin.
The Santa Clara Valley ground water basin is divided into two broad
areas: (1) the recharge zone or forebay, and (2) the confined area,
where the study area is located. The forebayoccurs along the
elevated edges of the basin where the basin receives its principal
recharge. The confined area is located in the flatter interior
portion of the basin and is stratified or divided in individual
beds separated by significant aquitards. The confined area is
divided into the upper and lower aquifer zones. The division is
formed by an extensive regional aquitard that occurs at depths
ranging from about 100 feet, near the confined area's southern
boundary, to about 150 to 250 feet in the center of the confined
area and beneath San Francisco Bay. Thickness of this regional
aquitard varies from about 20 feet to over 100 feet.
Local - Stratigraphy in the local study area is characterized by
interbedded and interfingering sands, silts and clays. These soils
were deposited in complex patterns by fluvial alluvial systems
draining the uplands to the south; sediments were deposited as the
streams flowed north toward the Bay.
The nomenclature applied to the water-bearing zones in the study
area is representative of the hydrogeology within the Santa Clara
Groundwater Basin. A number of shallow water-bearing zones are
separated from deeper zones by the thick persistent regional
aquitard. The shallow zones may be subdivided into a variety of
zones depending upon depth, lithology and lateral persistence.
These zones are frequently labeled as A and B aquifer zones or A
13
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FIGURE
2
-
.
IAI' .~1 '..", '. ~ "-
lIMO JlUO ~ ..",(' ~ -.:'.- \,
. t '1('0 - c_c- .- ~ - /.A ~' ...
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. J ," . .......,.:::....:..::::~;;:i;i;;;:::??rtfli~~rrt~\rt/~~ ),.
,,/ / ~~'i / / ~; I . ......;.;. :':':':':':':':':':':':':':". : '.:.:.:.: ':':':':':':':':':':':':':':':':':':':;:::':'.:. :,:,:,:,:,:,:,.,:,,-,,
~ .:{::;::;::::;;: .:::::ffit:::::;:;:;:::::::::::::. ;::::;::::.:":;;:;:;:;:;:;:;:;:;:;:;:;;;::;;;;::;:;:;:: ::;::.: :""':':'::~ /.
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~ ~ ...::::'W:~~:tm};;~r~_:::\:ili:i;": ~%til'~~~
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. < '/ ~ '/ ~/ ::::::~:~:~:~:~:~:~:'.:;~~~' '/ '"
~ Z0 // h "~':::::::::::::.'"
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t
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L$J CONtrlNED ZONE
rza RECH~AGE ZONE
A
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........ ...---
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"
SANTA CLARA
VALLEY
HYDROG~LOGIC FE I ,TURES
-------
and B aquifers. The deeper aquifer is commonly referred to as the
C aquifer and the clay layer separating the upper and lower water-
bearing aquifers is commonly referred to as the B~C aquitard.
Within the study area the shallowest water-bearing aquifer has been
identified as the A aquifer. The deeper water-bearing aquifer
within the study area has been subdivided into three water-bearing
aquifers, "B1 through B3, based on the depths at which major sand
units are encountered. The A aquifer occurs between five and 25
feet below ground surface (bgs). The 81 aquifer is. encountered
between 30 and 45 feet bgs, the B2 between 50 and 65 bgs, and the
B3 aquifer between 70 and 90 feet bgs. The groundwater gradient in
all identified aquifer zones is in a north-northeast direction.
1.6
WATER USE
Groundwater from this basin provides up to 50% of the municipal
drinking water for the 1.4 million residents of the Santa Clara
Valley. In 1989, groundwater accounted for approximately 128,000
of the 315,000 acre feet of drinking water delivered to Santa Clara
Valley Water District customers. Municipal water supply wells are
generally perforated in the lower aquifer zone.
Both the National Semiconductor and AMD-Arques sites were listed on
the National Priorities List (NPL) primarily because of the
potential threat from chemical" releases to the quality of this
valuable resource. The major concern associated with these sites
stems from the potential migration of contaminants in the upper
aquifer zones down to the lower aquifer zone through abandoned or
poorly sealed wells or natural conduits through aquitard material.
Vertical Conduit Studies - studies to determine the locations and
status of potential vertical conduit wells in the study area were
conducted 1986, 1987, and 1989. As a result of the 1986 and 1987
studies, a total of" 113 public and private wells that do, or did,
exist in a geogrqphical area, which includes the entire study area,
were identified. Of the 113 identified wells, the vast majority
" exist outside the area of groundwater contamination, are relatively
shallow (less than 100 feet deep) and do not penetrate the deep
aquifers, or documentation exists showing proper construction or
de~ommissioning.
The 1989 study, conducted by NSC, revealed that 22 of the
identified wells are considered potential vertical conduits. Of
these 22 identified wells, property owner or third party contacts
were completed for 11 of the wells; however, none of these contacts
yielded information about the existence or locations of wells. A
field program was performed to identify the locations of any buried
well casings. A visual reconnaissance identified that only 11 of
the 22 wells' appeared to be located in areas within the extent of
the groundwater plume and accessible for geophysical surveys. A
surface geophysical survey was performed to assess the existence
and locations of the 11 wells. Only one surface anomaly was
15
-:...... - -- ~- ... .
------
, ~'.-.
-------
detected and a downhole geophysical survey was conducted to verify
whether the anomaly was indicative of a well casing. The measured
data from this survey indicated that the magnetic anomaly appeared
to be from a shallow metallic object and not a metallic well
casing. As such, it appears that vertical conduit wells cannot be
identified as a problem in the study area.
Non-Conduit Deep Wells - Two deep water production wells exist
within the plume area: Well CWW 20-02 and the Hilton Well. The
City of Santa Clara owns and operates water production well CWW 20-
02, located near the intersection of Semiconductor Drive and Tahoe
Way, on the NSC facility. During the work week (Monday through
Friday), the well supplies water to NSC's deionized water system;
however, ten to twenty percent of the water produced by the well
goes to the City of Santa Clara and is used to supplement the City
water supply. According to the City of Santa Clara, water from
Well CWW 20-02 is blended with water from 20 other wells in the
distribution system.
Well CWW 20-02 was installed in October 1980. The well extends
from ground surface to a depth of 660 feet and is screened in eight
places across aquifers that range in depth from 265 to 639 feet.
The well has a sanitary seal that extends from ground surface to a
depth of 110 feet. The City of Santa Clara performs monthly
analyses on Well CWW 20-02. Cis-1,2 DCE has been detected at
concentrations ranging from 0.5 to 0.7 parts per billion (ppb) from
May 1986 through June 1989. This chemical was also detected in
November and December of 1989 at 0.5 ppb, and has been detected in
September 1990 and October 1990 at 0.7 and 0.5, respectively.
A second deep production well, the Hilton Well, is owned by the
Oakmead Lake Industrial Properties company and was installed on
March 24, 1976. The well is located in Subunit 3 at the Sunnyvale
Hilton Inn on Lakeside Drive, near Highway 101. The well is
operated infrequently and serves to provide water to an artificial
lake adjacent to the Hilton Inn. The well is 260 feet deep and is
screened across aquifers between 115 and 260 feet deep, with a
sanitary seal from ground surface to a depth of 50 feet. The well
was sampled annually from February 1982 to May 1989 and has since
been sampled quarterly. In 1985, ethylbenzene, xylenes, and PCE
were detected at concentrations of 10, 14, and 7 ppb, respectively.
In 1987 and 1988, cis-l,2-DCE was detected at concentrations of 8.5
and 4.9 ppb, respectively, and in May and July 1990, Freon 113 and
cis-l,2-DCE were detected at concentrations ranging from 0.8 to 1
ppb. No volatile organic compounds (VOCs) have been detected since
then.
The Regional Water Quality Control Board (RWQCB) Basin Plan
identifies potential beneficial uses of the shallow ground water
underlying and adjacent to the NSC and AMD-Arques Sites. These
beneficial uses include industrial process water supply, industrial
service water supply, municipal and domestic water supply and
16
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agricultural water supply. These are the same as the existing and
potential beneficial uses of the ground water in the Lower Aquifer
Zone. -
2.0
SITB HISTORY AND BNFORqEMBNT ACTIVITIBS
RBGULATORY AND BNFORCEMBNT HISTORY
2.1
State Reaulation of Sites - Contamination was discovered at the
National Semiconductor (NSC) and Advanced Micro Devices - Arques
(AMD-Arques) sites in 1982. Investigation and source control
measures were implemented early on by the Companies under
California Regional Water Quality Control Board (Region Two)
direction. state orders regulating Potentially Responsible Party
(PRP) activities at the sites were issued or amended in August
1986, September 1986, February 1988, and April 1989. National
Pollutant Discharge Elimination System (NPDES) permits were issued
by the RWQCB in'March 1987 (NSC's treatment system) and in February
1990 (AMD' s treatment system). These permi ts set treatment
standards for the effluent discharges - from the groundwater
extraction and treatment systems that have been installed to
control migration of chemicals in the subsurface.
Listina History and Onaoina Federal PartnershiD with State - Both
sites were proposed to the National Priority List (NPL) on October
15, 1984,.and both sites were listed July 22, 1987. The Regional
Water Quality Control Board (RWQCB) has remained the lead agency
for oversight of PRP work at these sites. These sites are two of
approximately twenty NPL sites in the Santa Clara Valley that are
regulated under RWQCB-lead pursuant to the South Bay Multi-site
Cooperative Agreement with EPA (EPA Assistance Agreement:
#V009403), which was established in October 1985.. Under this
agreement EPA and the RWQCB have implemented a major cooperative.
effort. involving the affected industries, local governments, and
state regulatory agencies in mUltiplePRP investigations and
cleanups at South Bay NPL sites. -
Identification of PotentiallY ResDonsible Parties - Pursuant to the
California Health and Safety Code Sections 25356.1 (c) and (d), the
State currently identifies the following potentially Responsible
Parties (PRPs) associated with the release of contaminants to the
subsurface at Operable Unit 1: NSC, AMD-Arques, HP (Hewlett
Packard), and UTC (United Technologies Corporation). qther
potentially responsible parties may be identified by the State in
the future. EPA has not performed a PRP search for these sites.
Aareements Amona PotentiallY ResDonsible Parties - NSC reports that
on September 14, 1987, NSC and UTC executed an agreement whereby
NSC assumed soil and groundwater cleanup responsibility for the
former UTC facility.
17
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2.2
HISTORY OF SITE INVESTIGATIONS
Subunit 1 - In early 1982, the RWQCB initiated a leak detection
program to define the extent of leakage from underground storage
tanks and pipes in the South Bay area. In response to the RWQCB's
leak detection program, NSC initiated a preliminary assessment of
soil and groundwater near its facility's underground solvent
storage tanks and acid neutralization sumps. After the preliminary
assessment was completed, NSC removed some of the tanks and sumps
and soil from some of the areas having elevated concentrations of
solvents. Additional tanks and sumps have been removed at the
facility since that time.
Soil sampling programs at the NSC facility began in 1982 and have
. been conducted as recently as December 1990 under RWQCB oversight,
to identify source areas for soil and ground water contamination.
In 1984 NSC installed an offsite extraction and treatment system to
control migration of site chemicals. Then in 1986 NSC installed
another extraction and treatment system approximately 1200 feet
downgradient of the NSC facility for additional control of chemical
migration in the subsurface. Treatment of extracted groundwater
consisted of air stripping under BAAQMD permit. This 1986 effort
was regulated under RWQCB orders and includes wells located on the
former UTC facility. .
At the former UTC facility, which is part of Subunit 1, UTC used
several outdoor areas for chemical drum storage and/or rocket
propellant testing. In addition, three underground flow-through
acid neutralization sumps were used. Investigations have been
performed between 1982 and 1986 under RWQCB direction on former UTC
property to identify potential source areas. In 1990 further soil
investigation identified the former locations of one acid
neutralization sump- abd two chemical storage areas which remain
source areas.
Subunit 2 - Monolithic Memories (subsequently AMD-Arques) also
responded to the 1982 South Bay leak detection program. They
initiated subsurface investigations at their -facility in 1982
because of suspected leakage from several underground chemical
solvent storage tanks and chemical handling areas used for qnsite
storage and/or treatment of waste solvents. Monolithic Memories
(MMI) subsequently removed soil from some of the areas having
elevated concentrations of solvents as well as some of the sumps
and tanks. -
In 1986, AMD installed an onsite A aquifer groundwater extraction
and treatment system to control contaminant migration in the
subsurface. In 1988 AMD expanded the onsite extraction and
treatment system to include groundwater extracted from the deeper
B aquifer in order to further control contaminant transport. The
treatment of extracted groundwater consists of air stripping under
BAAQMD permit. -
18
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soil sampling programs at AMD-Arques began in 1982 and have been
conducted as recently as November 1989, under RWQCB oversight, to
identify source areas for soil and groundwater contamination.
Subunit 3 - Subunit 3 does not contain any facilities that are
known sources of the solvent groundwater plume that emanates from
Subunits 1 and 2. Historically, NSC has taken responsibility for
the investigation of the extent of the commingled plume in Subunit
3. The investigation effort in this downgradient portion of the
contaminated area has been an ongoing part of the investigations
begun by NSC in 1982.
Besides the NSC, AMD-Arques, and former UTC facilities, there are
other facilities in the area that may have contriputed to the
groundwater pollution in Subunit 3 (see Figure 1). Operable Unit
2, with investigations currently underway, will address this aspect
of the study area contamination.
3.0
COMMUNITY RELATIONS
A community relations program haS been ongoing for all Santa Clara
Valley Superfund sites, including National Semiconductor and the
AMD-Arques sites. The RWQCB published a notice in the Mercury News
on June 12, 1991, announcing the Proposed Plan and the opportunity
for public comment at the Board Hearing of June 19, 1991 in
Oakland. The notice also announced the opportunity for. public
comment at an evening public meeting held at the Fairwood
Elementary School in Sunnyvale on June 27, 1991. A presentation of
the proPQsed final cleanup plan was made at both meetings. A 30-
day comment period was announced that would run from June 19 to
July 19, 1991. As a result of a request from a member of the
public, the comment period was extended until August 19, 1991 to
allow more time for public review.
Proposed Plan Fact Sheets were mailed in June (prior to the public
comment period) and hand-delivered to interested residents, local
government officials, and media representatives. The Proposed Plan
Fact Sheet described the site problems, the cleanup alternatives
that were evaluated, and explained the reasons for selecting the
proposed remedy. The Fact Sheet also announced the opportunity for
public comment at the Board Hearing in Oakland on June 19, 1991 and
at the Public Meeting in Sunnyvale on June 27, 1991. In addition,
this fact sheet described the availability of further information
at the Information Repository.
A Responsiveness Summary was prepared to address significant
comments received during the public comment period and appears in
Part III of this ROD. A future fact sheet will explain the Final
Cleanup and Abatement Order adopted by the RWQCB.
19
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4.0
SCOPE AND ROLE OF THE RESPONSE ACTION
4.1
SCOPE OF THE RESPONSE ACTION
The remedy selected and described in this ROD incorporates existing
groundwater extraction systems which have served to control
contaminant migration, and will expand the system to meet the
cleanup objectives for a final remedy. An evaluation of sump,
tank, and contaminated soil removal activities following discovery
shows that these early source control measures helped to prevent
migration of contaminants and that they are consistent with the
objectives of the final selected remedy.
Current Onaoina Groundwater Extraction - The NSC groundwater
extraction system is comprised of 45 A and B aquifer extraction
wells in Subunit 1. However, some of these wells are dry because
of water level declines. As of January 1991, 29 A and B aquifer
extraction wells were pumping water to the three NSC. treatment
systems (air strippers) at a total rate of 115 gpm.
At AMD there. are seven A aquifer extraction wells that were
constructed in 1986, and three B aquifer wells that were
constructed in 1988, which now are pumping groundwater to AMD's
treatment system (air stripper) in Subunit 2 at a total rate of 45
gpm.
In Subunit 3 NSC has installed three extraction wells along
Lakeside Drive, near Highway 101. These wells are not operating at
this time, but will deliver 80 gpm or extracted groundwater to the
ozone oxidation treatment system that is part of this selected
remedy.
All current groundwater extraction acti vi ties have been implemented
under RWQCB authority with the goal of controlling further
contaminant migration while ongoing site investigations -continued
to collect the data necessary for final remedy selection.
4.2
SELECTED RESPONSE ACTION
The selected final remedy for the National Semiconductor and
Advanced Micro Devices - Arques Operable unit 1 includes the
following elements:
o Groundwater extraction, to control further migration
of site chemicals in the aquifers and reduce chemical
concentrations until cleanup standards have been achieved.
o Treatment of extracted groundwater with air stripping
or ozone oxidation under Bay Area Air Quality Management
District BAAQMD permit or pursuant to OSWER Directive
9355.0-28.
20
.~.
-------
o Discharqe of extracted and treated groundwater to storm
sewers under National Pollutant Discharge Elimination System
(NPDES) permits, with some treated groundwater recycled as
facility process water.
o soil Vapor Extraction (SVE) will be employed where vadose
zone soils present a potential continuing source of
contamination to groundwater or where shallow soils
represent a health risk due to direct contact. Shallow
soils at the AND facility are contaminated with semi-
volatile compounds and may require removal if they do not
respond to SVE. SVE will be conducted pursuant to a
BAAQMD permit. .
o Institutional Controls prohibiting the use of the A and B
aquifer groundwater and for controlling activities that
'could endanger the public health or the environment.
In order to implement this final remedy for Operable Unit 1, the
currently operating extraction system will be expanded, and an
ozone oxidation treatment system will be added to the current air
stripper treatment systems. The air strippers and SVE will include
air emissions control (carbon treatment) if emissions exceed levels
currently permitted by the BAAQMD or. if required by QSWER Directive
9355.0-28. NPDES discharges will go to storm sewers which empty
into the Calabazas Creek.
Vadose and shallow soil contamination at these sites will be
addressed by SVE. Contingent upon the inability of SVE to address
low volitility compounds, some excavation and surface aeration of
contaminated soils will be performed. If it is determined that
this additional effort is necessary, a permit from the BAAQMD must
be obtained.
4.3
ROLE OF THE RESPONSE ACTION
The selected remedy for Operable Unit 1 addresses VOC (Volatile
Organic compounds)- contaminated groundwater in the Upper Aquifer
Zone and contaminated soils (mainly VOCs) on facility properties.
The primary concerns are: .
o further lateral migration of the coptaminant plume into
previously uncontaminated areas of a potential drinking
water supply;
o potential vertical migration of contaminated ground water
into the Lower Aquifer Zone that serves as a current source
of drinking water;
o direct contact with contaminated soil;
o and an ongoing chemical source from contaminated soils to
21
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groundwater.
The objective of the selected remedy is to remove and permanently
destroy the contaminants from both soils and groundwater or to
significantly reduce the toxicity, mobility or volume of hazardous
substances in both media. contaminated groundwater at the site
represents the primary risk at the site, and the remedy is intended
to return groundwater to its beneficial uses within a reasonable
period of time. Soil contamination at the site represents a
continuing source of groundwater contamination and represents the
principal threat at the site. This principal threat will be
addressed by the remedy. Thes~ response actions will greatly
reduce the possibility of contamination of current and potential
wat~r supplies.
5.0
SUKHARY OF SITE CHARACTERISTICS
5.1
SOIL AND GROUNDWATER
As previously described in section 1.2, of the Declaration,
Operable Unit ~ has been subdivided into three subunits as shown in
Figure 1 on page 11:
o Subunit 1 consists of the National Semiconductor Corporation
(NSC) facility at 2900 Semiconductor Drive, Santa Clara and
the former United Technologies corporation (UTC) facility at
1050 Arques Avenue, Sunnyvale, and all downgradient areas to
Arques Avenue.
o Subunit 2 consists of the Advanced Micro Devices - Argues
(AMD-Argues) facility, formerly Monolithic Memories, at .1165
and 1175 Argues Avenue, Sunnyvale.
o Subunit 3 consists of the downgradient area from Subunits 1
and 2 to the extent of the plume and Operable Unit 1,
approximately 1400 feet north of Highway 101.
The following--'" sections on soil. and groundwater highlight the
sources of contamination, the soil areas targeted for cleanup, and
the characterization of the aquifer contamination in the three
subunits of Operable Unit 1.
Soils - Soil contamination in Operable unit 1 has been attributed
to chemical releases from storage areas; leaks from sumps,
pipelines, and tanks; and chemical handling practices. Potential
source areas investigated have included a variety of acid waste
sumps and solvent tanks, leaks in chemical piping, and chemical
storage areas.
At the NSC facility (Subunit 1), investigations have identified 11
source areas that are included in the selected remedy for cleanup.
The principal organic chemicals detected in the soil at the NSC
22
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facility follow. The maximum historical values cited are orders of
magnitude higher than present conditions.
PCE 9,600 ppb
1,2-DCE - 930 ppb
1,1,1-TCA 150,000 ppb TCE 850 ppb
xylenes 3,300 ppm ethylbenzene 18,000 ppm
At the former UTC facility (Subunit 1) one acid neutralization sump
and two chemical storage areas have been identified as potential
sources of soil and groundwater contamination. These areas have
been included in the plans for cleanup also. The principal organic
chemicals detected in the soil at the former UTC facility follow:
1,1,1-TCA
1. 9 ppm
TCE
4.6 ppm
At the AMD-Arques facility (Subunit 2), three source areas that are
included for cleanup in the final plans have been identified. The
principal organic chemicals detected in the soil at the AMD
facility are ~olvents at a total concentration up to 400 ppm.
PCE
xylenes
TCE
chlorobenzene
1,2-DCE
In addition to the solvents, aromatic chemicals (PNAs) such as
naphthalene, pyrene, and phenol have been identified at the AMD
site up to 270 ppm. These PNAs are thought to have been imported
with fill material during past construction activities at the site.
They are detected in soils between two and five feet below surface.
Groundwater - Groundwater contamination in Operable Unit 1 is
believed to have been the result of chemical transport through
shallow and vadose zone soils from the various points of release,
or source areas, outlined in the previous section. The State of
California has detE[!rmined that the contaminated aquifers are a
potential drinking water supply. The chemicals found in Operable.
Unit 1 include halogenated and aromatic VOCs. Each subunit varies
with respect to the particular subset of these chemicals
identified. The approximate lateral extent of the Volatile Organic
Compound (VOC) plume is shown in Figure 1 on page 11. .
In Subunit 1, the following indicator chemicals are identified for
tracking the VOC plume:
cis-1,2-DCE
1,1,1-TCA
TCE
Freon 113
They are used as indicators for the VOC plume because they are
detected in a large number of wells, have elevated concentrations,
and are also found in wells downgradient of Subunit 1. These four
indicator chemicals are, or have been, present in the A, B1, and B2
aquifers. Aromatic VOCs are present in the A and B1 aquifers in
23
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Subunit 1 and immediately downgradient. Phenols are present in a
few A aquifer wells in Subunit 1. Analytical data indicate that
organic chemicals are not present in the 83 aquifer.
The highest current levels of groundwater pollution in Subunit 1
are listed below:
TCE. . . . . . . . . . . . 4200 ppb
1,2-DCE........6800 ppb
Freon 113 .....2000 ppb
ethylbenzene...9900 ppb
xylenes........11,000 ppb
Currently the groundwater pollution in Subunit 1 extends to a depth
. of up to 65 feet.
In Subuni t 2, the following indicator chemicals are used for
tracking the v6c plume:
PCE
TCE '
ciS-1,2-DCE
chlorobenzene
xylenes
These chemicals are used as indicators for the VOC plume because
they are detected in a large number of wells at elevated
concentrations. TCE and cis-1,2-DCE (also indicators for Subunit
1) are present in the A, 81 and B2 aquifers in Subunit 2 and
downgradient.in Subunit 3. '
The highest current- levels of groundwater pollution in Subunit 2
are listed below:
TCE.......950 ppb
1,2-DCE...1100 ppb
Currently, the groundwater contamination in Subunit 2 extends to
depths of up to 65 feet.
The same indicators used for Subunit 1 are used for Subunit 3 (cis-
1,2-DCE, 1,1,1-TCA, TCE and Freon 113). These chemicals are
detected in a large number of wells at elevated concentrations.
Analytical data indicate that organic chemicals are not present in
the B2 or B3 aquifer in Subunit 3. The four indicator chemicals
are, or have been, present in the A and 81 aquifers.
The highest current levels of groundwater pollution in ,Subunit 3
are reported as follows:
TCE.......510 ppb
1,2-DCE...1200 ppb
24
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Currently, the lateral and vertical extent of groundwater
contamination in Subunit 3 is approximately 1400 feet north of
Highway 101 and 45 feet below ground surface.
5.2.
AIR
Volatilization of groundwater contaminants and migration through
the vadose zone and into residential spaces was modeled as a part
of the Baseline Public Health Evaluation. The modeling predicted
an average 1 in 10 million and a maximum 1 in 1 million cancer risk
from this exposure pathway. Although the models do not predict
that the volatilization pathway poses any risk to the community,
soil gas sampling was performed in order to validate the model
predictions. There are several other VOC contaminated groundwater
Superfund sites in the Santa Clara Valley where the same concerns
have been raised by community members and are being addressed
similarly with collection of empirical data for model validation.
This pathway wtll be reevaluated as part of the five year review.
The sampling for this site showed the model to be conservative in
its assumptions; no detectable levels of contamination were found.
..
Emissions from the air strippers that are currently used as part of
the interim remedial action are regulated under a permit issued by
the BAAQMD.
6.0
SUMMARY OF SITE RISKS
6.1
HUMAN HEALTH RISKS
Two Baseline Public Health Evaluations (BPHE) have been conducted
for Operable Unit 1. One of them addresses Subunits 1 and 3, and
the other addresses Subunit 2. Both of these BPHEs have undergone
EPA review.and approval.
Risks were characterized in each of the BPHEs for pathways
involving soil, groundwater and air. As described in the National
Contingency Plan, the EPA acceptable cancer risk range is 1 X 10-4
to 1 X 10.6 for exposure to known or suspected carcinogens at
concentration levels that represent an excess upper bound lifetime
cancer risk to an individual. For noncarcinogenic effects, the
Hazard Index (HI) provides a useful reference point for gauging the
potential significance of mult.iple contaminant exposures within a
single medium or across media. EPA considers an HI of 1.0 or less
to be acceptable. A summary of each BPHE follows in the next
sections.
A summary of the carcinogenic and non-carcinogenic risks f9r the
three subunits can be found in Tables 3 through 5.
Subunits 1 and 3: BPHE Summary - The RWQCB BPHE for Subunits 1 and
3 identified the following "chemicals of concern": 23 organic
25
'-'-...-
-------
compounds for groundwater, 14 organic compounds and 6 metals for
soil, and 18 organic compounds for air. Further evaluation of the
soil data in the FS has resulted in the elimination of all the
metals as "chemicals of concern" because detected concentrations
fell within ranges that are considered background.
The "chemicals of concern"for soil and groundwater in Subunit 1
are listed in Table 1, and include the following compounds:
benzene
chloroform
1,1-DCA
TCE
1,1-DCE
1,2-DCE
Freon 113
xylenes
vinyl chloride
1,4-dichlorobenzene
PCE
pentachlorophenol
chloromethane
1,1,1-TCA
1,2-Dichlorobenzene
ethylbenzene
All of these chemicals are potentially toxic above certain
concentrations. Benzene and vinyl chloride are categorized as
known human carcinogens (EPA class A). Chloroform, 1,4-
dichlorobenzene, 1,1-DCA, PCE, TCE, and pentachlorophenol are
considered to be potential or probable human carcinogens (EPA class
B1 and B2).
The BPHE developed current and future exposure scenarios. The only
identified potential for a current complete exposure pathway was
indoor exposure to vapors migrating from the contaminated
groundwater in Subunit 3. This pathway was evaluated for residents
at the northern edge of the study area. These cancer risks and
health hazard assessments are based on estimates of the indoor air
concentrations of the chemicals of concern as predicted by
mathematical models. The predicted carcinogenic risk to residents
is estimated to be approximately one in ten million for the average
case and one in ~e million for the plausible maximum case. These
.risks fall within the acceptable 'range of carcinogenic risk
delineated in EPA regulation. . The model does not predict any
noncarcinogenic toxic effects from this exposure. Actual data
collected to support the model conclusions showed that no
det~ctable volatilization from groundwater to the surface is
occurring.
For the reasonable maximum exposure scenario, it was assumed that
Subunits 1 and 3 would be developed in the future for residential
use and that the groundwater in the A and B aquifers would be used
for domestic purposes. According to the BPHE, potential future
exposure routes in Subunit 3 might include ingestion of groundwater
containing the "chemicals of concern" (2 liters per day for 75
'years), inhalation of VOC vapors from groundwater during showering
or other domestic uses, and inhalation of VOC vapors originating
from the groundwater.
26
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Table 1
CHEMICALS AND MEDIA OF CONCERN
Subunits 1 and 3, Operable Unit 1
Santa Clara and sunnyvale, Santa Clara County
Chemical Name
Groundwater
Soil
Air
Acetone
Benzene
Chloroform
Chloromethane
4-Chloro-3-Methylphenol
1,2-Dichlorobenzene
1,4-Dichlorobenzene
1,1-Dichloroethane
1,1-Dichloroethene
cis-1,2-Dichloroethene
trans-1,2-Dichloroethene'
2,4-Dimethylphenol
2,4-Dinitrophenol
Ethylbenzene
Freon 113
2-Methyl-4,6-Dinitrophenol
4-Nitrophenol
Pentachlorophenol
Phenol
Tetrachloroethene
Toluene
Trichlorobenzene
1, 1, 1-Trichloroethane
Trichloroethene
Vinyl Chloride'
Xylenes (total)
x
x
x
x
x
x
x
x
x
x
x.
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Source: California Regional .Water Quality Control Board, San
Francisco Bay. Region Site Cleanup Requirements For National
Semiconductor Corporation and Advanced Micro Devices, Subunit 1,
Operable Unit 1. .
--...... -
-------
Table 2
CHEMICALS AND MEDIA OF CONCERN
Subunit 2, Operable Unit 1
Sunnyvale and Santa Clara, Santa Clara County
------------=--====----=========================================
Chemical Name
Groundwater
Soil
Chlorobenzene
1,2-DCA
1,2-DCB
l,l-DCE
. 1, 2 -DCE
Ethyl Benzene
Freon 113
PCE
TCA
TCE
Toluene
Vinyl Chloride
Xylenes
Polynuclear Aromatic
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
x
Hydrocarbons (PNAs)
x
x
=================================
Source: California Regional Water Quality Control Board, San
Francisco Bay Region site Cleanup Requirements For Advanced Micro
Devices and National Semiconductor Corporation, Subunit 2, Operable
Unit 1. .
~
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TABLE 3
SUMMARY OF POTENTIAL HEALTH RISKS
NATIONAL SEMICONDUCTOR CORPORATION SITE
Scenario
CURRENT-USE SCENARIOS
Inhalation of VOCs
migrating from off-site
groundwater into
residences:
-- north of 101
-- south of 101
FUTURE-USE SCENARIOS
Ingestion of ground-
water -- Aquifer A
Inhalation of VOCs --
in groundwater
Aquifer A
Potential
Excess
Cance:
Average
3 x 10"7
4 x 10'7
2 x 10'3
(1 x 10'3)
5 x 10'*
(4 x 10'*)
Upperbound
Lifetime
r Risks
Plausible
Maximum
5 x 10'6
3 x 10'6
9.6 x 10'1
(1 x 10'1)*
4 x 10*1
• (1 x 10'1)'
Hazard Index
Average Plausible
Maximum
a s
Ingestion of ground-
water - - Aquifer B
Inhalation of VOCs --
from groundwater
Aquifer B
Inhalation of chemicals
migrating from
on-site groundwater
into residences
3 x 10'5
4 x 10'5
7 x 10'5
(4 x 10-s)«
Inhalation of VOCs
migrating from off-site
groundwater into 8 x 10~5
residences (8 x lO'
1 x 10'3
2 x 10°
' x 10'*
(2 x 10"*)«
4 x 10'3
(4 x 10'3)«
<1
<1
<1
>1
<1
<1
<1
<1
• Total potential upperbound cancer risks omitting vinyl chloride possible
outlier value.
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TABLE 1/
(Agency Addendum for Advanced Micro Devices' RI &. FS Reports, Page 8 of 10)
CARCINOGENIC RISKS ASSOCIATED WITH PROPOSED GROUND WATER CLEANUP STANDARDS
Advanced Micro Devices and National Semiconductor Corporation
Subunit 2, Operable Unit I
Sunnyvale and Santa Clara, Santa Clara County
CHEMICAL CLEANUP CHRONIC ORAL INHALATION INGESTION INHALATION TOt' AL
STANDARD''' DAILY CANCER I'Ul'ENCY CANCER I'Ul'ENCY RISK RISK CARCI-
IPInl INTAKE FACTOR FACTOR (CDI-cPF J (CDI.CPF~ NOGENIC
(CDI)'" (CPF J (CPF~ RISK
Imalk.'.,1 l(malk.'dl,)"11 l(malltJ,.,)"'1
I, I-DichloroedUlne 5 5.71 £.05 . 0.091 - U&06 - U&06
Tdr8Chloroethcne 5 5.71£.05 0.051 0.0033 1.9&06 1.9&07 3.1&06
Trichloroelhene 5 5.71 £.05 0.011 0.017 6.3&07 9. 7E-07 1.6&06
Vinyl chloride 0.5 5.71 &06 1.90 0.295 1.1£45 1.7&06 1.3E-05
TOt' AL RISKS - - - - 2.0£.05 2.9&06 2.3E-05
(II
(2)
All cleanup standards are set at federal or California MCLs, whichever are lower.
CDI = (cleanup standard [mgn) . ingestion rate [I/day) . exposure duration [yrs). exposure frequency [days/yr» I (body wght [kg) . avging time [days))
cm = (cleanup standard [mg/l) . 2 . 30'. 365) I (10 . 27,375)
,i'
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//
TABLE S'
(Agency Addendum for Advanced Micro Devices' RI &. FS Reports, Page 9 of 10)
CHEMICAL CLEANUP CHRONIC ORAL INHALATION INGESTION INHALAnoN TUrAL
ST ANDARD'II DAILY REFERENCE DOSE REFERENCE DOSE HAZARD HAZARD HAZARD
(palll INTAKE (RIDJ (RID.) (CDIIRIDJ (CDIIR~ QUOTIENT
(CDI)'. ...Ita/." ...Ita/."
...lta/."
Chlombenzene 30 ..58&04 0.0'1 - 0.429 - 0.429
1,2-Dichlombenzene 6QIJt 1.71 E-03 0.09 0.04 0.019 0.043 0.062
1,l-DictaloroefMne , 1.43&04 0.10 0.10 0.014 0.001 0.015
I,I-Dichloroethene 6 1.71&04 O.OOIW" - 0.190 - 0.190
cl..I,2-Dichloroechene 6 1.71 &04 0.01 - 0.017 - 0.011
In-I,2-Dichloroelhene 10 U6&04 0.0'1 - 0.014 - 0.014
Elhylbenr.ene 68" 1.94E-03 0.10 0.286 0.019 0.007 0.026
F- 113 1200 3.4]E-4)2 JO 7.10 0.001 0.004 0.005
Telnchlorodhene , 1.4]&04 0.01 - 0.014 - 0.014
I,I,I-Trich~ne 200 '.71E-03 0.09 O.JO 0.063 0.019. 0.081
Trichloroelhene , 1.4]E-04 0.0074 - 0.019 - 0.019
X,lenel (10181) 17,. '.00E-03 2.00 0.087 0.003 0.057 0.060
1UI'AL HAZARD INDEX - - - - 0.801 0.131 0.933
NON-CARCINOGENIC RISKS ASSOCIATED WITH PROPOSED GROUND WATER CLEANUP STANDARDS
Advanced Micro Devices and National Semiconductor Corporation
Subunit 2, Operable Unit 1 .
Sunnyvale and Santa Clara, Santa Clara County
(I)
C2I
(3)
I
All cleanup standards are set at federal or California MCLs, whichever are lower, except for those noted with I superscript 2 C21,
Cleanup standards are set at one-tenth the federal or California MCLs, whichever are lower.
COf = (cleanup standard (mg/l) . ingestion rate (i/day) . exposure duration (yrs) . exposure frequency (days/yr» I (body wght (kg} . avging time (daysH
CDI = (cleanup standard (mgll) . 2 . 30 . 365) I (70 . 10,950). .
This value is one-tenth the oral reference. dose for I,I-Dichloroethene (RIDJIO = 0.009/10 = 0.00(9)
(~
-------
The calculated total risk for Subunits 1 and 3 is 2.6 X 10-3
carcinogenic risk (exceeding EPA's acceptable risk range) and a
noncarcinogenic hazard index exceeding 1 (indicating the potential
for adverse health effects to occur). The rationale underlying the
decision to take action to clean up Subunits 1 and 3 is based on
the potential human health risks that Subunits 1 and 3 pose.
Subunit 2: BPHE - The BPHE conducted for Subunit 2 (the AMD
facility) identified the following "chemicals of concern": 13
organic compounds for groundwater, and 24 organic compounds (eight
VOCs and sixteen polynuclear aromatics or PNAs) and four metals for
soil. These were identified based on toxicity and frequency of
detection for soil and groundwater data. Further evaluation of the
soil data in the FS has resulted in the elimination of all the
metals as "chemicals of concern" because detected concentrations
are within the range that is considered background for this area.
The "chemicals of concern" for soil and groundwater in Subunit 2
are listed in Table 2, and include vinyl chloride, 1,1-DCA, PCE,
TCE, 1,1-DCE, 1,2-DCE, 1,1,1-TCA, Freon 113, 1,2-Dichlorobenzene,
xylenes, ethylbenzene, chlorobenzene, and toluene. All of these
chemicals are potentially toxic above certain concentrations.
Vinyl chloride is categorized as a known human carcinogen (EPA
class A). 1,1-DCA, PCE, and TCE' are considered to be potential or
probable human carcinogens (EPA class B1 and B2).
The BPHE did not identify any current potential for completed
exposure pathways in Subunit 2. For the hypothetical future
exposure scenarios, it was assumed that the AMD facility would be
developed for residential use and that the groundwater in the A and
B aquifers would be used for domestic purposes. According to the
BPHE, potential future exposure routes at the AMD facility may
include ingestion 'of groundwater containing the chemicals of
concern, inhalat.,ion of VOC vapo.rs from groundwater during .showering
or other domestic uses, and inhalation of VOC vapors volatilizing
from the groundwater. .
The calculated total risk for Subunit 2, is 4.0 X 10-3 carcinogenic
risk (exceeding EPA's acceptable risk range) and a noncarcinogenic
hazard index equal to nine (indicating the potential for adverse
health effects to occur). The rationale underlying the decision to
take action to clean up Subunit 2 is based on the potential risks
that Subunit 2 poses.
6.2
ENVIRONMENTAL RISKS
Wildlife that may be present in the vicinity of the site includes
. raccoons, gophers, ground squirrels, rats, field mice, and a
variety of birds, including burrowing owls. The State of
California Department of Fish and Game has listed the burrowing owl
as a "species of special concern." The burrowing owl's primary
32
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habitat is grassland and open prairie.
exist in the immediate area.
Neither of these habitats
Two endangered species are reported to use South San Francisco Bay.
The California clapper rail and the salt marsh harvest mouse are
reported to exist in the. tidal marshes of the Bay and Bay shore,
located approximately 5 miles north of the NSC and AMD-Arques
sites. The endangered California brown pelican is occasionally
seen in the Bay Area, but does not nest in the South Bay. Ranges
of the endangered American peregrine falcon and southern bald eagle
include the Bay Area. The southern bald eagle does not use bay and
bayshore habitats, but the peregrine falcon has started to make a
comeback at some northern locations in San Francisco Bay.
The AMD-Arques and National Semiconductor sites do not qonstitute
critical habitat for endangered species nor do they include or
affect any "wetlands." Be'cause the facilities are covered with
pavement or structures, direct-contact exposures to contaminants of
concern in soil on these sites by wildlife are unlikely. Impacts
to wildlife are expected to be minimal. .
6.3
CONCLUSION
If not addressed by implementing the response action selected in
this ROD, the actual or threatened releases of hazardous substances
from the Advanced Micro Devices - Arques and National Semiconductor
Superfund sites may present an imminent. and substantial
endangerment to the public health, welfare, or environment. Given
that a variety of the contaminants detected at the site pose
significant health risks as carcinogens or as noncarcinogens and
that complete exposure pathways are possible under .future 'use
scenarios, EPA has determined that remediation is warranted.
7.0
DESCRIPTION AND CONSIDERATION OF ALTERNATIVES
7.1 APPLICABLE OR RELEVANT AND APPROPRIATE REQUIREMENTS (ARARS)
FOR ALTERHATIvtS CONSIDERED AT AND-ARQUES AND NSC
The following sections detail the ARARs which are referenced as
part of the Al ternati ve descriptions in Section 7.2 below. The key
ARARs for this site are the drinking water standards, the State
anti-degradation policy, regulations governing volatile air
emissions from treatment operations, and Federal regulations
governing disposal of hazardous wastes. The groundwater and soil'
cleanup standards that have been set as protective for Operable
Unit 1 of the AMD-Arques and NSC sites are presented in Table 3 on
page 38.
33
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Section 1412 of the Safe Drinkina Water Act. 42 U.S.C. Section
300a-1
Under section 1412 of the Safe Drinking Water Act, EPA is required
to set Maximum Contaminant Level Goals (MCLGs) for ground and
surface water. Under CERCLA, MCLGs that are set at levels above
zero shall be attained by remedial actions for ground or surface
water that are current or potential sources of drinking water,
where the MCLGs are relevant and appropriate under the
circumstances of the release based on the factors in S300. 400
(g) (2) .
The appropriate remedial goal for each indicator chemical in ground
water is the MCLG (if not equal to zero), the federal MCL, or the
State MCL, whichever is most stringent.
California DeDartment of Health Services Drinkina Water Action
Levels (DWALs)
California Department of Health Services (DHS) DWALs are health-
based concentration limits set by the DHS to limit public exposure
to substances not yet regulated by promulgated standards. They are
advisory standards that apply at the tap for public water supplies.
ARARs with more stringent requirements take precedence over these
DWALs. Phenol and 2, 4-dimethylphenol are. the only compounds
present in Operable Unit 1 for which a DWAL will be applied. These
compounds have no current federal or state promulgated standards.
California's Resolution 68-16
California's "Statement of Policy with Respect to Maintaining High
Quality of Waters. in California," Resolution 68-16, has been
determined by EPA to be an ARAR. The policy requires maintenanc~
of existing water quality unless it is demonstrated that a change
will benefit the people of the State, will not unreasonably affect
present or potential uses, and will not result in water quality
less than that prescribed by other State policies. .
For Operable Unit 1 at the AMD-Arques and NSC sites, the affected
aquifers have been classified as potential sources of drinking
water. Generally, EPA has considered that anti-degradation
policies, such as Resolution 68-16, require prevention of further
degradation of beneficial use of the groundwater, during and at
completion of the response action. In this case, Resolution 68-16
would require control of the plume to prevent further degradation
of uncontaminated areas in the aquifer, and cleanup to drinking
water standards before remediation could be considered complete.
National Pollutant Discharae Elimination Svstem (NPDES)
NPDES substantive permit requirements and/or RWQCB Waste Discharge
Requirements (WDRs) are potential ARARs for effluent discharges.
34
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The effluent limitations and monitoring requirements of an NPDES
permit or WDRs legally apply to point source discharges such as
those from a treatment system with an outfall to surface
water or storm drains. The RWQCB established effluent discharge
limitations and permit requirements are based on Water Quality
Standards set forth in the San Francisco Bay Regional Basin Plan.
There will be five treatment systems with discharges to storm
drains at the AMD-Arques and NSC sites they will be regulated under
NPDES permits.
EPA Office of Solid Waste and Emergency Response fOSWER) Directive
9355.0-28
OSWER Directive 9355.0-28 "Control of Air Emissions from Superfund
Groundwater Air Strippers at Superfund Groundwater Sites" applies
to future remedial decisions at Superfund sites in ozone non-
attainment areas. "Future remedial decisions" include Records of
Decisions (RODs), Significant Differences to a ROD and Consent
Decrees. AMD-Arques and NSC are in an ozone non-attainment area.
This directive requires such sites to control total volatile
organic compound emissions from air strippers and soil vapor
extractors to fifteen pounds per day per facility. This directive
is not -an ARAR, but is a TBC. ARARs with more stringent
requirements take precedence over the directive.
Bav Area Air Quality Management District (BAAQMD) Regulation 8.
Rule 47
Bay Area Air Quality Management District Board of Directors adopted
Regulation 8, Rule 47. This rule is entitled "Air Stripping and
Soil Vapor Extraction Operations" and applies to new and modified
operations. The rule consists of two standards:
o Individual air stripping and soil vapor extraction
operations emitting benzene, vinyl chloride,
perchloroethylene, methylene chloride and/or
trichloroethylene are required to control emissions by at
least ninety percent by weight. Operations emitting less
than one pound per day of these compounds are exempt from
this requirement if they pass a District risk screen.
o Individual air stripping and soil vapor extraction
operations emitting greater than fifteen pounds per day of
organic compounds other than those listed above are required
to control emissions by at least ninety percent by weight.
Regulation 8, Rule 47 is an ARAR for the implementation of the
remedy at the AMD-Arques and NSC sites, which will both employ air
.stripping and soil vapor extraction technologies.
35
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Bay Area Air Quality Management District (BAAOMD) Regulation 8.
Rule 40
Bay Area Air Quality Management District Board of Directors adopted
Regulation 8, Rule 40. This rule is entitled "Aeration of
Contaminated Soil and Removal of Underground Storage Tanks." since
surface aeration of contaminated soils is considered in one of the
AMD-Argues site cleanup alternatives as a contingency measure
pending the unsuccessful operation of Soil Vapor Extraction in
certain shallow soils that are contaminated with lower volatility
compounds, this ARAR may potentially apply if the contingency is
implemented. This regulation would limit the emission of organic
compounds from soil.
Resource Conservation Recovery Act fRCRA) Land Disposal
Restrictions.
The contaminants in groundwater and soil at the AMD-Arques and NSC
sites include spent solvents that are RCRA listed wastes.
Adsorbents and other materials used for remediation of groundwater
VOCs, such as activated carbon, chemical-adsorbing resins, or other
materials used in the treatment of ground water or air will contain
the chemicals after use. RCRA land disposal restrictions are not
applicable, but are relevant and appropriate to disposal of
treatment media due to the presence of constituents which are
sufficiently similar to RCRA wastes.
Additionally, if "placement" of excavated soil occurs at these
sites, the Land Disposal Restrictions (LDRs) will apply.
Alternative 3 considers excavation and surface aeration of
contaminated soils as a contingency if soils are unresponsive to
SVE treatment. If the surface aeration is conducted within the
area of contamination (areal extent of contiguous contamination),
the LDRs are not triggered. However, if excavated soil is moved to
another location, they will apply, and the soil will have to be
managed as a hazardous waste.
7.2 OPERABLE UNIT 1 ALTERNATIVES FOR THE AMD-ARQUES AND NSC SITES
The following sections describes the remedial alternatives that
were considered for addressing contamination within Operable Unit
1 of the AMD-Arques and NSC sites. The three alternatives consist
of the following:
o Alternative 1 - No Action
o Alternative 2 - Site-wide Groundwater Extraction and
Treatment, Soil Vapor Extraction (SVE) in
Subunit 2
o Alternative 3 - Site-wide Groundwater Extraction and
Treatment, Soil Vapor Extraction (SVE) in
36
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Subunits 1 and 2, .With a Contingency to
Excavate and Aerate Shallow Soils
Unresponsive to SVE .
The site-specific cleanup standards set for the groundwater and
soils are presented in. Table 6. Shown also are the state and
federal drinking water standards. Note that several of the site-
specific cleanup standards are lower than the state and federal
standards. These numbers have been reduced to address risk of
exposure from multiple contaminants, i.e., to achieve a protective
Hazard Index that is equal to, or less than 1, and a calculated
cancer risk within the acceptable risk range of 10'6 to 10'4.
A discussion of the uncertainty in achieving the cleanup standards
is presented in Section 7.3 following this section.
7.2.1 Al~erna~ive 1 - No Ac~ion
General DescriDtion - The "No Action" alternative assumes that the
groundwater extraction and treatment efforts initiated in 198~, a~d
conducted to. date, are an adequate response. The groundwater
extraction and treatment system currently in operation would be
shut down. Contaminant concentrations would be reduced by natural
attenuation as the plume continued to migrate towards San Francisco
Bay. Groundwater monitoring would continue in order to track
chemical migration and to evaluate the effectiveness of the "No
Action" alternative. Institutional controls and deed restrictions
would be required to prevent well construction in areas of the
contaminated aquifers where an unnaceptable risk of exposure to
polluted groundwater remains.
How Well Does the Alternative Meet ARARs/CleanuD Obiectives -
Modeling conducted in the evaluation of this alternative shows that
it would require more than 200 years for natural attenuation to
achieve the cleanup standards (-Table'3, page 39) for the 'AMD-Arques
. and NSC Operable Unit 1. Chemical specific Applicable or Relevant
and Appropriate Requirements (ARARs) - the Federal and state MCLs
would not be met within an acceptable time period, and the
state's anti-degradation policy, Resolution 68-16 (which is an ARAR
at. this site) will be violated by allowing further degradation of
a potential drinking water supply.
Risk Evaluations and Cleanu9 Time - Under this alternative, the
baseline risk of 4 x 10~3 and the Hazard index (HI) of 9 in Subunit
2 is not appreciably reduced in a reasonable time frame. And the
baseline risks of 3 x 10-3 and HI > 1 are not reduced effectively
in Subunits 1 and 3 within reasonable time periods.
Costs - Total present worth cost (using a 10% discount rate and
assuming 30 years of operation) for the "No Action" alternative is
approximately $3.2 million.
37
~~._.-'. --
,~..- -
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Table 6
Cleanup Standards and ARARs'
AMD/Arques and NSC sites Operable Unit 1
Chemical Name
Federal
MCLG2
(ppb) 3
Federal
MCLlo
(1m.Q )
State
MCL or
AL5
Groundwater
Benzene 0 5 1
Chlorobenzene 100 100 30
Chloroform N/A 100 N/A
Chloromethane N/A N/A 110
4-Chloro-
3-methylphenol N/A N/A N/A
1,2-Dichlorobenzene 600 600 1307
1,1-Dichloroet~ane N/A N/A 5
1,1-Dichloroethylene 7 7 6
cis-1,2-
Dichloroethylene 70 70 6
trans-1,2-
Dichloroethylene 100 10
2,4-Dimethylphenol N/A . N/A 4007
2,4-Dinitrophenol N/A N/A N/A
Ethylbenzene 700 700 680
Freon 113 N/A N/A 1200
2-Methyl-4,6-
dinitrophenol N/A N/A N/A
Pentachlorophenol 0 1 307
Phenol N/A N/A 57
Tetrachloroethylene 0 5 5
Trichloroethylene 0 5 5
Vinyl Chloride 0 2 0.5
Xylene (total) 10,000 10,000 1,750
1,4 Dichlorobenzene 75 5
1,1,1-Trichloroethane 200
Soil
Total VOCs
Polynuclear Aromatic
Hydrocarbons (PNAs) N/A
N/A
1
2
3
4
5
6
7
N / A -. d
- N/A
N/A
. .N/A
N/A
Site
Cleanur
Std.
1
30
5
5
7
60
5
6
46
5
686
1200
1
1
5
5
5
0.5
1756
~~ "c.
1ppm
10ppm
Not Available
California State Water Resources Control Board Policy Number
68-16 is also ARAR
MCLG = Maximum Contaminant Level Goals
ppb = parts per billion
MCL = Maximum Contaminant Level, Current or Proposed
AL = California Action Level (TBC) .
Site Specific Health Protective Standards set considering
ARARs and calculated cancer risks and Hazard Indices..
This number is a California Action Level
-------
7.2.2 Alternative 2 - Groundwater Extraction and Treatment, Soil
Vapor Extraction (SVE) in subunit 2
General Description - This alternative combines the following major
components: (1) expansion of the current groundwater extraction and
air stripping system, (2) soil remediation in Subunit 2 only, using
Soil Vapor Extraction (SVE) , (3) groundwater monitoring to track
effectiveness of extraction system, and (4) deed restrictions
preventing access to contaminated groundwater and soil during
remediation. The expanded groundwater system would be designed to
capture and reduce groundwater contamination in Operable Unit 1
until cleanup standards have bee~ met. Included in this plan is
the capture of the downgradient end of the plume, which currently
is ~ncontrolled.
This alternative would contain migration of contaminants in the
polluted aquifers, and it would treat soils in Subunit 2 that would
otherwise provide an ongoing source of groundwater contamination.
However, contaminated soils would remain untreated in Subunit 1.
How Well Does Alternative 2 meet ARARs/Cleanup Obiectives
Modeling shows that the estimated time to meet the groundwater
cleanup standards for the AMD-Arques and NSC sites, is greater than
100 years under this alternative (despite the fact that Subunit 2
might be able to meet the standards much sooner - 30 to 100 years).
The cleanup standards (which are set for protectiveness and to meet
federal and state requirements) would not be met within an
acceptable time period except within Subunit 2 (the AMD facility).
The State's anti-degradation policy, Resolution 68~16 (which is an
~ for these sites) is met, however, because further degradation
of a potential drinking water supply will be prevented. ---
This Alternative can meet ARARs for air emissions (See Section
- 7.1) . If meeting the BAAQMD permit levels requires emissions
control such as activated carbon, disposal of spent carbon (if not
regenerated) will have to be managed in accordance with Resource
Conservation Recovery Act (RCRA) Land Disposal Restrictions (LDRs).
Carbon used as/the-final stage of' the ozone oxidation groundwater
treatment system in Subunit 3 will also fall in this category of
materials that must be managed as a RCRA waste.
National Pollutant Discharge Elimination System (NPDES) substantive
permit requirements and/or RWQCB Waste Discharge Requirements
(WDRs) are ARARs for effluent discharges. Effluent from the
groundwater treatment systems employed in this alternative is.
subject to both of these ARARs which include regulation of
discharge limits, points of compliance, and monitoring frequencies.
Risk Evaluations and Cleanup Time - Under this alternative, the
baseline risk of 4 x 10-3 and the HI of 9 in Subunit 2 may be
reduced to 2 x 10-5 and an HI = 0.93, in a 30 - 100 year time frame.
But, in Subunits 1 and 3, the baseline risks of 3 x 10-3 and HI >
39
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--
1 will not be appreciably reduced within an acceptable time frame
(greater than 100 years).
To summarize, Alternative 2 can provide a cleanup that achieves
acceptable risk levels within a reasonable period of time for only
one portion of Operable unit 1. Othe~ areas of Operable Unit 1
remain above acceptable risk levels for greater than 100 years.
Costs - The present worth cost of Alternative 2 (using a 10%
discount rate and assuming 30 years of operation) is $5.5 million.
7.2.3 Alternative 3 - Groundwater Extraction and Treatment, soil
Vapor Extraction (SVE) in subunits 1 and 2, with a contingency to
Excavate and Aerate Shallow Soils unresponsive to SVE .
General Description - This alternative combines the following major
components: (1) expansion of the current groundwater extraction and
treatment system, (2) soil remediation in Subunits 1 and 2, using
Soil Vapor Extraction (SVE) , (3) groundwater monitoring to track
effectiveness of extraction system, and (4) deed restrictions
preventing access to contaminated groundwater and soil during
remediation. The expanded groundwater system (identical to
Alternative 2) would be designed to capture and reduce groundwater
contamination in Operable Unit 1, including the downgradient end of
the plume that is currently uncontrolled, until cleanup standards
have been.met.
The only difference between Alternatives 2 and 3 is that soils in
Subunit 1 will be treated in addition to those in Subunit 2. Note
that this difference significantly reduces cleanup time from
greater than 100 years to a 50 - 100 year range for Operable Unit
1. .
Just as with Alternative
migration of contaminants
further than Alternative 2
Subunits 1 and 2 that would
groundwater contamination.
2, this alternative would contain'
in the polluted aquifers. ' It goes
in that it would treat soils in bo~h
otherwise provide an ongoing source of
How Well Does Alternative 3 Meet ARARs/Cleanup Obiectives - The key
ARARs with which Alternative 3 must comply are almost the same as
those for Alternative 2 since the only difference between the two
alternatives is an expansion of the areas of soil to be treated,
rather than a difference in technologies being applied. However,
if certain shallow soils that are contaminated with lower
volatility compounds do not respond well to SVE, there is a
contingency plan to excavate and aerate these soils at the surface.
If this occurs, air emissions during excavation and aeration will
be regulated under the BAAQMD Regulation 8, Rule 40 and
UNACCEPTABLE restrictions will apply if "placement" of contaminated
soil occurs (see page 34, RCRA Land Disposal Restrictions).
40
J
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Modeling shows that the estimated time to meet the. groundwater
cleanup standards for the AMD-Arques and NSC sites if Alternative
3 is implemented, is within 50 to 100 years. The cleanup standards
would be met within an acceptable time period. The State's anti-
degradation policy, Resolution 68-16 (which is an ARAR for these
sites) is also met because further degradation of a potential
drinking water supply will be prevented.
This Alternative can meet ARARs for air emissions (See Section
7.1) . If meeting the BAAQMD permit levels requires emissions
control such as activated carbon, disposal of spent carbon (if not
regenerated) will have to be managed in accordance with Resource
Conservation Recovery Act (RCRA) Land Disposal Restrictions (LDRs).
Carbon used as the final stage of the ozone oxidation groundwater
treatment system in Subunit 3 will also fall in this category of
materials that must be managed as a RCRA waste.
National Pollutant Discharge Elimination System (NPDES) substantive
permit requirements and/or RWQCB Waste Discharge Requirements
(WDRs) are ARARs for effluent discharges. Effluent from the
groundwater treatment systems employed in this alternative is
subject to both of the~e ARARs which include regulation of
discharge limits, points of compliance, and monitoring frequencies.
Risk Evaluations and CleanuD Time - In Subunits 1 and 3, the
baseline risks of 3 x 10-3 and HI > 1 may be reduced to 3 x 10-5 and
an HI.= .87, in a 50 - 100 year time frame if Alternative 3 is
implemented.
To summarize, Alternative 3 can provide a cleanup that achieves an
acceptable risk level within a reasonable period of time (50 - 100
years).
Costs - The present worth cost of Alternative 3 (using a 10%
discount rate and assuming 30 years of operation) is $8.4 million.
7.3
UNCERTAINTY IN ACHIEVING CLEANUP STANDARDS
The goal of the final remedy is to restore groundwater to its
beneficial uses by meeting the cleanup standards presented in Table
3. Based on information obtained during the Remedial Investigation
and on a careful analysis of all remedial alternatives, EPA and the
RWQCB believe that the selected remedy will achieve this goal.
However, studies suggest that groundwater extraction and treatment
will not be, in all cases, completely successful in reducing
contaminants to health-based groundwater quality standards using
this approach. It may become apparent, during implementation or
operation of the groundwater extraction system and its
modifications, that contaminant levels have ceased to decline and
are remaining constant at levels higher than the cleanup standards
over some portion of the plume. In such a case, the system
41
-------
.
performance standards and/or the remedy may be reevaluated by EPA.
Additional discussion pertaining to this issue occurs in Section
9.2. .
8.0
COMPARATIVE ANALYSIS OF ALTERNATIVES
The alternatives were evaluated using nine component criteria.
These nine criteria are derived from requirements contained in the
National Contingency Plan (NCP) and CERCLA Sections 121 (b) and
121(c). A comparative discussion of how the alternatives perform
when measured against each of the nine criteria follows.
1. PROTECTION OF HUMAN HEALTH AND THE ENVIRONMENT
Alternative 1, the "No Action" alternative does not achieve
protectiveness within an acceptable timeframe (i.e., it would take
more than two. hundred years for natural attenuation to meet
standards). Without active site restoration efforts, potential
drinking water supplies are threatened with levels of contamination
that exceed acceptable risks. AdditionallY, soils in Subunit 2
that contain Polynuclear Aromatic (PNAs) chemicals would constitute
a potentiar for unnaceptable cancer risk due to direct contact if
the site is not cleaned up and is then developed for residential
use.
Alternative 2 addresses soil contamination through treatment in
Subunit 2 and thereby reduces the potential for direct contact risk
posed by PNAs at the site. Pump and treat systems contain and
reduce the groundwater contamination, mitigating some of the threat
to potential drinking water supplies. However, without further
soil remediation than is contemplated by this alternative,
contaminated soils in Subunit 1 will continue to serve as an
ongoing source of contamination to the affected aquifers, extending
the cleanup time to longer than 100 years. Hydraulic control of
the plume reduces the risk of further contamination of the
groundwater, however unacceptable levels of risk remain in a
potential drinking water supply for a long time.
Alternative 3 actively addresses both soil and groundwater
contamination at the sites through treatment such that risk due to
direct contact with these media is reduced to acceptable levels
within 50 to 100 years.
2. COMPLIANCE WITH ARARS
Both Alternatives 2 and 3 would attain all pertinent ARARS iden-
tified in section 7. The Safe Drinking Water Act MCLs and
California Department of Health Services DWALs would be achieved by
extracting ground water contaminated above these levels. NPDES
permit requirements would be met by proper design and operation of
the treatment systems. ARARs that are related to air emissions
from the soil vapor extraction, air strippers, or excavation
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activities can be met with proper system design and implementation.
The RCRA land disposal restrictions would apply to the spent carbon
from Alternatives 2 and 3, if stripper or vapor extraction
emissions control involving gas-phase activated carbon is required.
They would also apply if the excavation contingency is implemented
and "placement" of contaminated soil occurs.
The drinking water ARARS would not be attained by Alternative 1 for
an unacceptably long period of time. Compliance with Resolution
68-16 would not be achieved since the groundwater contaminants
would unreasonably affect the potential uses of the upper aquifers.
RCRA land disposal restrictions, NPDES requirements, BAAQMD
Regulation 8, and OSWER Directive 9355.0-28 would not apply to
Alternative 1 since it does not employ any treatment.
3. REDUCTION OF TOXICITY. MOBILITY. OR VOLUME THROUGH
TREATMENT
Both Alternatives 2 and 3 have the potential to reduce the
toxicity, mobility, and volume of soil and groundwater contaminants
by removing them and treating them. If air emissions require
controls, contaminants would be destroyed during carbon
regeneration, making any future release of the removed contaminants
impossible. If emissions controls are not required (they would
have to be low enough to meet BAAQMD permit requirements for this
to be the case), contaminants will be transferred to the air where
their toxicity, mobility, and volume actually increase. It should
be noted that a risk evaluation is performed as part of the permit
decision to require controls on air ,emissions.
Both Alternativ~s 2 and 3 employ an ozone oxidation treatment
system which will treat a portion (80 gpm) of the extracted
groundwater. (The rest, 160 gpm, is treated with air strippers.)
This technology, which will be combined with a carbon filtration at
the final stage of the treatment train, will achieve. complete
destruction of th~contaminants'extracted from the A and B aquifers
,in Subunit 3.
Alternative 2 would take a longer time to achieve these reductions
in toxicity, mobility, and volume through treatment than would
Alternative 3 (up to 50 years longer).
Alternative 1 does nothing to reduce toxicity, mobility, or volume
through treatment.
4. LONG-TERM EFFECTIVENESS AND PERMANENCE
Alternatives 2 and 3 include groundwater extraction which is in-
tended to reduce the level of contamination in the A and B Aquifer
Zones to the cleanup standards indicated in Table 3 on page 38.
Thus, potential risks to the community are minimized. To ensure
that the magnitude of residual risks are minimized, the performance
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of the groundwater extraction system would be monitored on a
regular basis and adjusted as warranted by the performance data
collected during operation for both of these alternatives.
Treatment by air stripping provided by Alternatives 2 and 3 is
reliable for the long-term removal of VOCs from the ground water.
Treatment by ozone-oxidation, as is planned in Alternatives 2 and
3, is also reliable and considered even more permanent since nearly
complete destruction of the contaminants would be achieved. It
should be noted again, of course, that if air stripper emissions
exceed threshold levels in the BAAQMD regulations, emissions
controls will be required. Carbon adsorption would constitute the
control technology, and the carbon regeneration process would
provide complete destruction through thermal treatment.
Alternative 1, "no action," does not provide long-term
effectiveness.
5. SHORT-TERM EFFECTIVENESS
There are no anticipated adverse impacts on human health and the
environment that are posed during the construction and operation of
the remedies that are part of Alternatives 2 and 3. Institutional
controls will preclude residential development in areas where soil
is contaminated, as well as preventing construction of water supply
wells in the affected aquifers. These institutional controls will
prevent direct contact with contaminants in groundwater and soils.
Air emissions from the treatment systems will be regulated by
BAAQMD permit and controlled with carbon if required. NPDES
requirements will ensure that discharged effluent from treatment
systems meets permit requirements as well.
6. IMPLEMENTABILITY
There are no technical concerns regarding the implementability of
Alternatives 2 and 3. Institutional controls required in Alter-
natives 1, 2, and 3 are administratively feasible.
7. COST
Alternative 1, the "no action" option, which does include long term
groundwater monitoring and deed restrictions but"~~no active
remediation work, has a present worth of $3.2 million.
Alternative 2, which actively addresses groundwater contamination
and some of the soils in Operable Unit 1, in addition to long-term
monitoring and deed restrictions, has a present worth of $5.5
million.
Alternative 3, actively addresses groundwater contamination and
soil contamination at each of the facilities in Subunits 1 and 2 in
Operable Unit 1 (also includes monitoring and deed restriction),
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has a present worth of $8.4 million.
It can be seen that as more protective measures are taken in each
successive alternative, that the cost increases incrementally. The
groundwater cleanup is the same for Alternatives 2 and 3, therefore
the additional soil cleanup work in Alternative 3 increases the
cost accordingly. It may be noted that this cost is the cost
associated with a significant reduction in the time needed to
achieve cleanup standards (Alternative 2 takes more than 200 years
at $9.9 million; Alternative 3 takes from 50 to 100 years at $11.6
million).
These present worth costs have been calculated assuming a 30-year
operation period and a ten percent discount rate.
8. SUPPORT AGENCY ACCEPTANCE
The Regional Water Quality Control Board (RWQCB) has maintained the
lead agency for oversight of PRP work at the Advanced Micro Devices
- Argues and National Semiconductor sites. EPA has actually played
the support agency role throughout the RI/FS process. These sites
are two of approximately twenty NPL sites in the Santa Clara Valley
that are regulated under RWQCB-lead pursuant to the South Bay
Multi-Site Cooperative Agreement with EPA (EPA Assistance
Agreement: #V009403), which was established in October 1985. Under
this agreement EPA and the RWQCB have worked in a close partnership
to develop the proposed plan for the AMD-Arques and NSC sites. The
RWQCB has recommended the plan, which EPA has reviewed and
considered in selecting this final remedy.
9. COMMUNITY ACCEPTANCE
The Proposed Plan was presented to the communities of Santa Clara
and Sunnyvale in a fact sheet and at a public meeting. [No
technical comments were submitted regarding the alternatives.
Other comments received are addressed in the Responsiveness
Summary.]
9.0 THE SELECTED REMEDY
9.1 DESCRIPTION
The selected final remedy for the National Semiconductor and
Advanced Micro Devices - Argues Operable Unit l includes the
following elements:
o Groundwater extraction, to control further migration
of site chemicals in the contaminated aquifers and reduce
chemical concentrations until cleanup standards have been
achieved (Carcinogenic Risk = 3 x 10"5; HI < l) .
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o Treatment of extracted groundwater with air stripping
or ozone oxidation under a Bay Area Air Quality Management
District BAAQMD permit or pursuant to OSWER Directive
9355.0-28.
o Discharge of extracted and treated groundwater to storm
sewers under National Pollutant Discharge Elimination System
(NPDES) permits.
o 80il Vapor Extraction (SVE) with carbon adsorption to
control emissions if required under BAAQMD permit
requirements or OSWER Directive 9355.0-28 will be employed
where vadose zone soils present a potential continuing
source of contamination to groundwater or where shallow
soils represent a health risk due to direct contact. Some
shallow soils are contaminated with less volatile compounds
and may require removal and surface aeration if they do not
respond 'to SVE.
o Institutional Controls prohibiting the use of the A and B
aquifer groundwater and for controlling activities that
could endanger the public health or the environment.
In order to implement this final remedy for Operable Unit 1, the
currently operating extraction system will be expanded, and an
ozone oxidation treatment system will be added to the current air
stripper treatment systems. The air strippers will include air
emissions control (carbon treatment) if emissions exceed levels
currently .permitted by the BAAQMD (one pound per day). NPDES
discharges will go to storm sewers which empty into the Calabazas
Creek.
Vadose and shallow soil contamination at these sites will be
addressed by SVE. Contingent upon the success of the SVE effort in
areas that contain lower volatility compounds, some excavation and
surface aeration of contaminated soils will be performed. If it is
determined that this additional effort is necessary, a permit from
the BAAQMD must be obtained.
It should be noted that the expanded groundwater extraction system
which is a part of the remedy for Operable Unit 1, will be designed
to capture all downgradient plume migration that may be coming from
both Operable Unit~ 1 and 2.
9.2
uncertainty in the Remedy
The goal of this remedial action is to restore the groundwater to
its beneficial use, which is, at this site, a potential source of
drinking water. Based on information obtained during the RI and on
a careful analysis of all remedial alternatives, EPA and the RWQCB
believe that the selected remedy will achieve this goal. It may
become apparent, during implementation or operation of the
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groundwater extraction system and its modifications, that
contaminant levels have ceased to decline and are remaining con-
stant at levels higher than the cleanup standards over some portion
of the plume. In such a case, the system performance standards
and/or the remedy 'may be reevaluated by EPA.
The selected remedy will include groundwater extraction for an
estimated period of 50 to 100 years, during which the system's
performance will be carefully monitored on a regular basis and
adjusted as warranted by the performance data collected during
operation. Modifications may include any or all of the following:
a) at individual wells where cleanup standards have been attained,
pumping may be discontinued;
b) alternating pumping at wells to eliminate stagnation points;
c) pulse pumping to allow aquifer equilibration and' to allow
adsorbed contaminants to partition into ground water; and
d) installation of additional extraction wells to facilitate or
accelerate cleanup of the .contaminant plume.
To ensure that cleanup standards continue to be 'maintained, the
aquifer will be monitored at those wells where pumping has ceased
on an occurrence of every 5 years following discontinuation of
groundwater extraction.
10.0
STATUTORY DETERMINATIONS
The selected remedy will comply with section 121 of CERCLA. The
selected remedy is protective of human health and the environment.
Contaminated groundwater and soils will be restored to health
protective levels once cleanup standards have been achieved, and
until that occurs, direct contact exposure to contaminated media
will be prevented with institutional controls. The. selected
response actions comply with Federal and state requirements that
are legally applicable, or relevant and appropriate; primarily the
drinking water standards (Federal and state MCLs), Bay Area Air
Quality Management District permit requirements for air emissions,
and the National Pollutant Discharge Elimination System
requirements for discharge of treated effluent.
These remedial actions address the principal risks at the National
Semiconductor and Advanced Micro Devices - Arques sites (Operable
Unit 1) by removing and treating the contamination in soils
(primarily soil vapor extraction), and by removing and treating
contaminants in ground water (extraction with air stripper and
ozone oxidation treatment), thereby significantly reducing the
toxicity, mobility or volume of hazardous substances in both media
through treatment. Using ozone oxidation treatment satisfies the
statutory preference for permanent solutions and remedies that
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1-
employ treatment as a principal element.
An evaluation of the alternatives considered shows the selected
remedy to be a cost effective response. Although the cost of the
selected remedy is $1.7 million more than the other active
remediation alternative considered, that additional cost reduces
the time necessary to achieve cleanup standards from more than 100
years to a 50 to 100-year time frame.
Because the remedy may require 50 to 100 years to achieve cleanup
standards, a five-year review, pursuant to CERCLA Section 121, 42
U.S.C. section 9621, will be conducted at least once every five
years after initiation of the remedial action to ensure that the
ongoing remedial action continues to provide adequate protection of
human health and the environment.
11.0
DOCUMENTATION OP SIGNIPICANT CHANGES
There were no significant changes between the preferred alternative
and the Record of Decision. .
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PART III.
RESPONSIVENESS SUMMARY
1.0
INTRODUCTION
This section of the Record of Decision contains agency responses to
all significant verbal and written comments submitted to RWQCB or
EPA staff during the 60-day public comment period and at the
Community Meeting held Jun 27, 1991. This ROD does not contain any
significant changes to the remedy that was made available for
public comment and described in the Proposed Plan Fact Sheet and
the RWQCB orders.
The public comment period began with a public meeting of the ex-
ecutive-board of the RWQCB on June 19, 1991 and ended 60 days later
on August 19, I991.
2.0
RESPONSES TO COMMENT
The RWQCB is the lead agency for the Advanced Micro Devices -
Arques and National Semiconductor sites and, as the lead, received
public comment. RWQCB and EPA have worked together in the
preparation of the Responsiveness Summary (Attachment A) and EPA
has approved all of the Responses.
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